Synthesis of sulfonated polyketone membranes by a direct sulfonation reaction and their properties

Abstract In this study, sulfonated polyketone cation exchange (SPOK) membranes were prepared by a direct sulfonation method and evaluated according to the concentration of sulfonating agent, reaction time and reaction temperature. The physicochemical properties of these membranes were measured to confirm their optimal synthetic conditions. The sulfur content in the SPOK membranes increased with increasing sulfonating agent concentration, reaction time and reaction temperature. The ion exchange capacity, water uptake and swelling ratio of these membranes increased with increasing sulfur content. The highest ion exchange capacity for the membranes was 1.01 meq/g. From the measured electrical properties, the electrical resistance showed a tendency to decrease with increasing sulfonation conversion, and the lowest electrical resistance was 0.4 Ω cm2 when the sulfonation conversion was 59.6%. To evaluate the possible application of the SPOK membranes to membrane capacitive deionization (MCDI) modules, their chemical resistance, durability and tensile strength were measured. The performance-limiting conditions for the tensile strength were 0.3 wt% chlorosulfonic acid (CSA)/CF, 20 °C and 60 min.